Fence Calculator
Posts, rails, pickets and concrete bags for a fence from its length, post spacing and gates — Quikrete-based bag counts, picket spacing and a materials cost.
Fence Calculator: with the default inputs, posts is 14.
Total of all runs, including gate openings.
8 ft on centre for wood with 16-ft rails; 6 ft for heavy privacy panels or windy sites.
3–4 ft for a walk gate, 10–12 ft for a drive gate (built as a double).
2 for fences up to 5 ft; 3 for 6-ft privacy fences.
Line posts plus an end post for each run and two posts per gate.
- Sections (bays)
- 12
- Rails
- 24
- Pickets
- 192
- Concrete bags (80 lb)
- 21
- Fenced length (excluding gates)
- 96 ft
- Actual post spacing
- 8 ftFenced length ÷ sections, so the bays come out even.
- Materials cost
- $0.00
Assumptions
- Posts = sections + runs, where each gate splits the fence into another run; corners don't add posts.
- Concrete per post defaults to Quikrete's 1½ bags for a 10 × 24-in hole; adjust for deeper gate and privacy-fence holes.
- Pickets are counted for a single layer; shadowbox fences roughly double it.
| Picket | Gap | Per 8-ft bay | Per 100 ft |
|---|---|---|---|
| 1×6 (5½ in) | butted | 17.5 | 219 |
| 1×6 (5½ in) | ½ in | 16 | 200 |
| 1×6 (5½ in) | 2 in | 12.8 | 160 |
| 1×4 (3½ in) | butted | 27.4 | 343 |
| 1×4 (3½ in) | 1½ in | 19.2 | 240 |
| 1×4 (3½ in) | 3 in | 14.8 | 185 |
Board-on-board (shadowbox) fences use about 1.8× the butted count.
How this is worked out
The formula
Fenced length = total length − gates × gate width Sections = fenced length ÷ post spacing, rounded up Posts = sections + number of runs (runs = gates + 1) Rails = sections × rails per section Pickets = fenced length ÷ (picket width + gap), rounded up Concrete bags = posts × bags per post
Open How it’s calculated above to see this worked through with your own numbers.
What you enter
- Total fence length
- Total of all runs, including gate openings.in ft, yd, m · 0 or more · defaults to 100
- Post spacing
- 8 ft on centre for wood with 16-ft rails; 6 ft for heavy privacy panels or windy sites.in ft, in, m, cm · from 0.5 to 20 · defaults to 8
- Gates
- A number.from 0 to 50 · whole numbers only · defaults to 1
- Gate width
- 3–4 ft for a walk gate, 10–12 ft for a drive gate (built as a double).in ft, in, m, cm · 0 or more · defaults to 4
- Rails per section
- 2 for fences up to 5 ft; 3 for 6-ft privacy fences.from 0 to 6 · whole numbers only · defaults to 2
- Picket width(under More options)
- A '1×6' picket is 5½ in; a '1×4' is 3½ in. Set 0 for a rail or panel fence with no pickets.in in, cm, mm · 0 or more · defaults to 5.5
- Gap between pickets(under More options)
- 0 for a tight privacy fence (boards shrink, leaving gaps); 1½–3 in for a picket fence.in in, cm, mm · 0 or more · defaults to 0.5
- Concrete bags per post (80 lb)(under More options)
- Quikrete: a 10-in hole, 2 ft deep, around a 4×4 takes about 1½ bags; 12 in × 3 ft for a 6-ft privacy fence takes 3.from 0 to 10 · defaults to 1.5
- Price per post(under More options)
- A number.in dollars · 0 or more · defaults to 0
- Price per rail(under More options)
- A number.in dollars · 0 or more · defaults to 0
- Price per picket(under More options)
- A number.in dollars · 0 or more · defaults to 0
- Price per concrete bag(under More options)
- A number.in dollars · 0 or more · defaults to 0
What you get back
- Postsmain answer
- Line posts plus an end post for each run and two posts per gate.
- Sections (bays)
- Rails
- Pickets
- Concrete bags (80 lb)
- Fenced length (excluding gates)
- Actual post spacing
- Fenced length ÷ sections, so the bays come out even.
- Materials cost
What this assumes
- Posts = sections + runs, where each gate splits the fence into another run; corners don't add posts.
- Concrete per post defaults to Quikrete's 1½ bags for a 10 × 24-in hole; adjust for deeper gate and privacy-fence holes.
- Pickets are counted for a single layer; shadowbox fences roughly double it.
About this calculator
A fence takeoff is mostly counting: how many bays, one more post than bays for each straight run, two or three rails per bay, and pickets by the linear foot. The details that trip people up are gates (each one adds two posts and removes a bay), corners, and concrete. This calculator handles the gates and the concrete and gives you a materials list you can price at the yard.
Post spacing
Eight feet on centre is the standard for wood: rails come in 16-ft lengths, so each rail spans two bays and the joints land on posts. Drop to 6 ft for heavy 6-ft privacy panels, in high-wind areas, or with vinyl (check the panel width — vinyl systems are often 6 or 8 ft exactly and don't cut well). The calculator rounds bays up and shows the actual spacing that makes them come out even, which looks far better than one short bay at the end.
Corners and runs
A corner post is just a line post that turns; it doesn't change the count. Gates do: each gate splits the fence into another run, and each run needs its own end post, so posts = bays + runs. Gate posts should be set deeper (36 in) and ideally in a bigger hole, and anything over 5 ft wide wants a double gate or steel posts.
Concrete
Quikrete's guidance for a 4×4 post in a 10-in hole 2 ft deep is about 1½ 80-lb bags; a 12-in hole 3 ft deep for a 6-ft privacy fence takes about 3. Set posts a third of their height in the ground, below frost line, on a few inches of gravel for drainage. Fast-setting mix goes in dry and is watered in place — no mixing — which is why fence crews use it.
Pickets
Pickets per foot depend only on board width plus gap. A "1×6" dog-ear picket is 5½ in wide; butted tight, that's 2.18 per foot or about 218 per 100 ft. Add a ½-in gap and it drops to 200. Wet pressure-treated boards shrink ¼–⅜ in as they dry, so a fence installed tight will open up on its own — plan for it. Board-on-board (shadowbox) fences need roughly 1.8× the butted count.
Reading the results
Posts, rails, pickets and bags are all rounded up. Enter prices under More options for a materials subtotal; hardware (screws or ring-shank nails, hinges, latch, post caps) typically adds 10–15% on top of lumber.
Frequently asked questions
▸How many fence posts do I need for 100 feet?
With posts 8 ft apart and no gates, 100 ÷ 8 rounds up to 13 sections, so 14 posts. Add one post for each gate (a gate splits the run in two and each run needs its own end post).
▸How far apart should fence posts be?
8 ft on centre for most wood fences, because rails are 16 ft. Use 6 ft for tall solid privacy fences, windy sites, or where the vinyl or metal panel system dictates it.
▸How many bags of concrete per fence post?
About 1½ 80-lb bags for a 4×4 in a 10-in hole 2 ft deep, and about 3 bags for a 12-in hole 3 ft deep. Gate posts get the bigger hole.
▸How many pickets do I need per foot of fence?
Divide 12 by the picket width plus gap in inches. Butted 5½-in pickets: 2.18 per foot (218 per 100 ft). With a 2-in gap: 1.6 per foot. 3½-in pickets with a 2½-in gap: 2 per foot.
▸How deep should fence posts be set?
A third of the post's above-ground height, and at least 2 ft — 3 ft for 6-ft privacy fences and all gate posts. Go below the frost line in cold climates or the posts will heave.
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